Bluetooth: Send HCI_Read_Clock_Offset before disconnecting

When the connection is in master role and it is going to be
disconnected based on the disconnection timeout, then send
the HCI_Read_Clock_Offset command in an attempt to update the
clock offset value in the inquiry cache.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>